Did you ever ask yourself why the bar on an electric train's overhead contact system doesn't wear out in a couple of days?
It's the same reason the rotary switch contact does.
Electric train's pantograph uses
carbon strips, softer than copper- like in a brushed DC motor commutator. But I see your point about the physics.
Thickness of the PCB copper compared with the wiper metal, I thought around 1/10 and thinner would lose. The wear model says it's hardness and force.
Another factor I notice is switch diameter makes the far outside (ring) path longer so the inner rings (wipers) don't wear as much.
Just looking at it to see why the cheap meters rotary switches did poorly. They have to redesign their wiper, less force it seems.